New Zealand’s Christchurch Hospital evaluates efficacy of Active Breathing Coordinator-assisted DIBH radiotherapy of left-sided breast cancer
Concerned about the long-term implications to heart health during breast cancer radiotherapy, Christchurch Hospital (Christchurch, New Zealand) acquired Elekta’s Active Breathing Coordinator™ (ABC) to facilitate Deep Inspiration Breath-hold (DIBH) radiotherapy for women with left-sided breast cancer. The New Zealand Breast Cancer Foundation (NZBF) funded the hospital’s acquisition of ABC, in addition to a 15-patient pilot trial that will lay the groundwork for a clinical ABC-assisted DIBH service.
The risks associated with cardiac irradiation have been examined extensively, including a recent patient-based case-control study of nearly 2,200 women who underwent radiotherapy for breast cancer between 1958 and 2001.1 Cardiac irradiation can result in major damage to the heart, including diffuse myocardial interstitial fibrosis, ischemia, pericardial thickening, valvular fibrosis and accelerated atherosclerosis. These pathological changes can produce multiple clinical complications, including coronary artery disease, pericarditis, cardiomyopathy and valvular heart disease.2
“Many of these problems are very much long-term issues,” concedes Melissa James, MD, Christchurch Hospital radiation oncologist. “We’ve audited our 12-year data on cardiac toxicity and haven’t really seen much of a difference, but the thought is that cardiac irradiation probably increases one’s risk of dying of ischemic heart disease by about one percent at 15 years, so the risks are likely small. However, the 2,200-patient case control study indicated that the risk of coronary artery disease is linearly related to the main heart dose, so that for every Gy of radiation, the patient potentially increases her risk of ischemic heart disease by about 7.5 percent.”1
She adds that according to the study there is no apparent threshold or “safe” dose.1 For example, doctors can’t affirm that a 20 Gy dose to the coronary artery is harmless and 40 Gy is a problem.
“That’s why we’re very eager to decrease the potential risk by moving the heart down and out of the radiation beam’s path with a deep inspiration breath-hold,” Dr. James says. “Active Breathing Coordinator ensures patients can perform DIBH correctly and consistently.”
Active Breathing Coordinator is linked to one of Christchurch Hospital’s three Elekta Synergy® linear accelerators through the Response™ gating interface, enabling automated gated breath-hold treatments to be delivered. The Response interface is also integrated with the center’s new Versa HD™ system, which began clinical treatments in September 2016.
“We now have a seamless workflow across the treatment machines,” Dr. James says.
Christchurch Hospital clinicians preferred an assisted breath-hold technique with Active Breathing Coordinator versus using a voluntary patient breath-hold method.
“Our feeling was that ABC with Response gating would provide a more reproducible, auditable technique, and that it would give more control to the patient,” she observes.
Christchurch Hospital treats about 250 breast cancer patients per year with curative intent. Approximately 46 percent of these patients have left-sided breast cancer. According to NZBF statistics, 3,000 New Zealand women are diagnosed with breast cancer each year, resulting in 600 deaths annually and making it the top-ranked cause of cancer death among women in the country.
Christchurch Hospital, the only public hospital in New Zealand with Active Breathing Coordinator, launched its pilot DIBH program on March 10. By June 6, the department had scanned six patients for program eligibility, of which three showed there would be a significant enough improvement in their main heart dose to treat with ABC-assisted DIBH (see sidebar ABC-DIBH workflow).
A patient’s suitability for the technique is determined by comparing the separation of the heart and breast – and therefore the dose the heart will receive – between a free-breathing scan and DIBH scan on the CT and linear accelerator, respectively.
“Our patients have actually loved it. It gives them a sense of control and participation in their treatment. They can watch the little graph of their breath and see the green bar that shows when they need to hold it,” she says. “Overall, there is a sense that patients are concerned about the toxicity of radiation to their heart and if there’s anything available that can potentially decrease that toxicity, they’re very motivated to use it.”
“For the three patients who weren’t eligible, their heart was nowhere near the radiation beam even on the free-breathing scan. The main heart dose was improved by such a small amount that we ended up not using DIBH for them,” Dr. James recalls. “About 30 percent of patients will fall into this category, along with those who can’t hold their breath or who find the equipment claustrophobic. However, 70 percent will likely benefit from DIBH. For example, the latest patient’s main heart dose was 7 Gy on a free-breathing scan, while the main heart dose on DIBH was just 1.6 Gy. For some patients, DIBH makes a very big difference in the dose the heart will receive.”
In Christchurch Hospital’s experience so far, Dr. James reports that patient acceptance of the Active Breathing Coordinator apparatus and process has been high.
Radiotherapist Stephanie Farrell checks the breathing machine.
“We’re determined to make the ABC-assisted DIBH service a success and I am certain it will be,” she adds. “Radiation therapy is such an important treatment for women with breast cancer so we need to make it as safe as possible for patients with left-sided cancer.”
The NZBCF-funded pilot trial will give Christchurch Hospital radiation oncologists insight into what the clinical ABC-assisted DIBH program will involve.
“We’re collecting a lot of data on the time it takes to coach patients, the time required for the CT scan and how much treatment system time is needed,” she says. “The hope is we can use the data from these 15 patients to work out selection criteria for the general population of our cancer patients and how we can fit the clinical program into our workflow.
Inspired by the promise of the DIBH program, the hospital administration has agreed to use its own funds to purchase a second Active Breathing Coordinator.